Objects follow each other on a curve path
Create your object.

Cerate a curve and shape it to the path you want the other objects to follow.

Make sure they have their origins on the same place.

Select the object and add a Follow Path constraint. Set the curve as target. Your object will move to the beginning of the curve. Then animate the offset value to make the object travel along the curve.


For several object you can use an array modifier and set the number of clones you need on the array. 

Then add a curve modifier after the array modifier, selecting the curve as object. Then move the object on the X axis.